Best way to communicate cocktail-but-ties-not-required/casual-but-no-jeans?

I know there's lots of etiquette online, and I've searched through prior posts here, but just want some examples of what language others have used.

We're having the event at an urban lounge space, very nice but not ballroom formal. We want guests to be comfortable, but polished? I just KNOW that "semi-formal" or "cocktail" attire will sound too stuffy and intimidating for both of our families, but "dressy casual" or "smart casual" will definitely be interpreted as jeans and t-shirt (as long as they don't have holes).

What language have others used to capture this in-between vibe? We're kind of leaning towards "cocktail casual" or "casual semi-formal"? Also, honestly, I don't really care if someone wants to wear a full ballgown or jeans or whatever, we've just had family asking us about the dresscode already.

Bonus points if you can offer a similar Spanish translation, lol.